Method of electroslag welding

ABSTRACT

A method of electroslag welding for use in the electroslag welding of high tensile strength members formed of low alloy steels of the family of steels which includes American Society of Testing Materials designation ASTM A516-76. The welding electrode used in the method has a chemical composition in which the carbon content and contaminants have been reduced to the very minimum possible, resulting in greater impact strength of the electroslag weld deposit. The welding electrode includes constituents of manganese, silicon, nickel and iron. The nickel and manganese content of the electrode are so proportioned as to compensate for loss of tensile strength in the electroslag weld deposit which would otherwise be caused by the minimal carbon content of the welding electrode, this proportioning of the nickel and manganese content of the welding electrode also maximizing impact strength and ductility of the weld deposit. When the electrode is used for the electroslag welding of low alloy, high tensile strength steel members, such as steels of the ASTM A516-76 family, the resulting electroslag weld deposit has a characteristic microstructure resulting in good tensile strength, high impact strength, and good ductility characteristics over a wide range of dilution of the weld deposit by the base metal, all without the necessity of an expensive and energy-consuming post-weld &#34;normalizing&#34; heat treatment as has been required in the prior art.

This is a division, of application Ser. No. 914,360, filed June 12,1978.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of electroslag welding.

2. Description of the Prior Art

Difficulties have been encountered in the prior art when attempting tojoin by welding members formed of low alloy, high tensile strengthsteels of the family of steels which includes American Society ofTesting Materials designations ASTM A516-76 (boiler or pressure vesseltype steel), ASTM A572-76 (structural plate steel) and ASTM A216-75(cast steel). In the prior art, when it has been attempted to provide anelectroslag weld between steel members of the family of low alloy, hightensile strength steels such as those described, the resultingelectroslag weld between the high tensile strength members has resultedin two basic problems, as follows:

(1) loss of impact strength in the weld deposit, i.e., poor resistanceof the weld to low stress brittle fracture; and

(2) low ductility of the weld.

The foregoing described undesirable characteristics of electroslag weldsbetween members of low alloy, high tensile strength materials such asthose enumerated could be overcome in the prior art only by the use of aprolonged post-weld "normalizing" high temperature heat treatment of thetotal welded part with subsequent cooling of the welded member in air orliquid. The purpose of this prior art post-weld normalizing heattreatment of the total welded part subsequent to the completion of theweld is to improve to acceptable values the mechanical properties of theweld deposit, including the tensile strength, impact strength, andductility of the weld deposit. Typically, the prior art normalizing heattreatment just mentioned is conducted at a temperature such as 1600degrees F. for a time period such as for four hours, after which thewelded member is cooled by liquid or air to a temperature such as 400degrees F.

It is obvious that the post-weld "normalizing" heat treatment requiredin the prior art in connection with welds in the ASTM A516-76 family ofsteels as just described is extremely expensive due both to furnace costand to fuel cost, and to such an extent that such cost is prohibitive.

To the best of my knowledge, prior to my invention there was no weldingelectrode known or available which could be used for the electroslagwelding of steels of the ASTM A516-76 family in which the resultingelectroslag weld deposit did not require the post-weld high temperaturenormalizing heat treatment hereinbefore described in order to obtainacceptable mechanical properties in the weld deposit.

In addition to the "normalizing" post-weld heat treatment just describedwhich was necessary in the prior art to obtain acceptable mechanicalproperties when welding low alloy, high tensile strength steel membersof the type hereinbefore described, it is also the general practice toprovide a stress relief heat treatment at a temperature such as 1150degrees F. The purpose of the stress relief treatment is to equalize thetensile and compressive stresses set up during the welding operation.This stress relief treatment just described is standard practicesubsequent to the completion of a weld and is utilized in welded membersproduced by use of the electrode and welding method of the presentinvention. However, as will be pointed out in more detail hereinafter,use of the welding electrode and welding method of the present inventioneliminates the need for the extremely expensive and energy consuminghigh temperature (such as 1600 degrees F.) post-weld "normalizing" heattreatment of welded parts which has been required in the prior art forelectroslag welds between low alloy, high tensile strength steels of thetype hereinbefore described.

A problem which has presented itself in the prior art in connection withthe formulation of welding electrode chemistry is the fact that a changein the electrode chemistry which tended to increase the impact strengthof the resulting electroslag weld, such as a decrease in the carboncontent of the welding electrode, at the same time tended to decreasethe tensile strength of the resulting electroslag weld to anunacceptable value; and conversely, a change in the electrode chemistry,such as an increase in the carbon content of the electrode, which tendsto increase the tensile strength of the resulting electroslag weld atthe same time tends to decrease the impact strength of the resultingelectroslag weld.

In this specification, in order to achieve brevity of expression, theabbreviation ASTM will be used to designate "American Society of TestingMaterials." Also, the expression "A516-76 family" will be used todesignate low alloy, high tensile strength steels of any of the typesand ASTM designations just enumerated (i.e., ASTM A516-76, ASTM A572-76and ASTM A216-75). Also, the abbreviation "PSI" will be used todesignate "pounds per square inch."

STATEMENT OF THE INVENTION

Accordingly, it is an object of the present invention to provide amethod of electroslag welding which has particular utility in connectionwith, although not necessarily restricted to, use in welding low alloy,high tensile strength steels of the family of steels which includes ASTMA516-76 steel and in which the resulting weld deposit or weld nugget hasgood tensile strength, high impact strength and good ductilitycharacteristics, all without the necessity of an expensive and energyconsuming post-weld "normalizing" heat treatment as has been required inthe prior art.

In achievement of these objectives, there is provided in accordance withthe invention a method of electroslag welding which has particularutility for use in the electroslag welding of members formed of lowalloy high tensile strength steels of the family of steels whichincludes American Society of Testing Materials designation ASTM A516-76.The welding electrode used in the method has a chemical composition inwhich the carbon content and contaminants have been reduced to the veryminimum possible, resulting in greater impact strength of theelectroslag weld deposit. The welding electrode includes constituents ofmanganese, silicon, nickel and iron. The nickel and manganese content ofthe electrode are so proportioned as to compensate for loss of tensilestrength in the electroslag weld deposit which would otherwise be causedby the minimal carbon content of the welding electrode, thisproportioning of the nickel and manganese content of the weldingelectrode also maximizing the impact strength and ductility of the welddeposit. When the electrode is used for the electroslag welding of lowalloy, high tensile strength steel members, such as steels of the ASTMA516-76 family, the resulting electroslag weld deposit has acharacteristic microstructure resulting in good tensile strength, highimpact strength, and good ductility characteristics over a wide range ofdilutions of the weld deposit by the base metal, all without thenecessity of an expensive and energy-consuming post-weld "normalizing"heat treatment as has been required in the prior art.

Further objects and advantages of the invention will become apparentfrom the following description taken in conjunction with theaccompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an electroslag welding process using anonconsumable nozzle;

FIG. 2 is a view taken along line II--II of FIG. 1 showing a crosssection of the welding wire or electrode;

FIG. 3 is a diagrammatic view of an electroslag welding process using aconsumable nozzle and showing the consumable nozzle and the wire-likeelectrode in a position corresponding to the beginning of theelectroslag weld;

FIG. 3a is a diagrammatic view similar to FIG. 3 but showing theconsumable nozzle and the wire-like electrode in a positioncorresponding to a partially completed weld deposit;

FIG. 4 is a view in horizontal cross section taken along line IV--IV ofFIG. 1 of the weld deposit of FIG. 1; FIG. 4 also shows the locationfrom which round tensile specimens of the type shown in FIG. 6 areremoved from the electroslag weld deposit for use in making tests oftensile strength, yield strength, and percent elongation of the welddeposit;

FIG. 5 is a graph in which tensile stress on the weld deposit is plottedagainst strain or elongation of the weld deposit;

FIG. 6 is a perspective view of a round tensile specimen of the typeused for making tests of tensile strength, yield strength, and percentelongation of the weld deposit;

FIG. 7 is a perspective view of the region of an electroslag welddeposit showing how a plurality of "sheets" of specimens are removedfrom the weld deposit for use in making bend tests on the electroslagweld, similar "sheets" being used for obtaining specimens for the Charpyimpact test, and also for obtaining reduced section tensile specimens;

FIG. 8 is a perspective view of one of the specimen "sheets" of FIG. 7used for providing bend test specimens;

FIG. 9 is a view showing a "sheet" from which specimens are removed onwhich Charpy impact tests are performed to test the resistance of theelectroslag weld deposit to low stress brittle fracture in accordancewith procedures established by the American Society of MechanicalEngineers and by the American Welding Society;

FIG. 10 is a perspective view of a specimen shown in FIG. 9 used formaking Charpy impact tests on the weld deposit;

FIG. 11 is a view showing a "sheet" from which a reduced section tensilespecimen is removed for use in making tests of tensile strength, yieldstrength, and percent elongation of the weld deposit;

FIG. 12 is a perspective view of the reduced section tensile specimenshown in FIG. 11;

FIG. 13 is a microphotograph of the microstructure, magnified 250 times,of the weld deposit identified as No. N-17;

FIG. 14 is a microphotograph of the microstructure, magnified 250 times,of the weld deposit identified as No. N-18;

FIG. 15 is a microphotograph of the microstructure, magnified 250 times,of the weld deposit identified as No. N-19; and

FIG. 16 is a microphotograph of the microstructure, magnified 250 times,of the weld deposit identified as No. N-20.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the schematic view of FIG. 1, there are shown twovertically positioned metal members respectively indicated at 10A and10B and separated by the joint gap indicated at G. The gap G normally isof uniform width for the entire vertical height of members 10A and 10B.In the illustrated embodiment, the two metal members 10A, 10B which areto be welded together by an electroslag weld deposit are made of lowalloy, high tensile strength steel of the family of steels whichincludes American Society of Testing Materials designation ASTM A-516-76as hereinbefore defined.

The apparatus used for the electroslag welding operation includes ahollow tubular nozzle member formed of electrically conductive materialand generally indicated at 12 and a wire-like welding electrode 14having a chemical composition in accordance with the invention as willbe described hereinafter. Nozzle 12 in the embodiment of FIG. 1 is ofthe nonconsumable type (i.e.--nozzle 12 is not consumed during thewelding operation). The wire-like welding electrode 14 may typically bea tubular member 1/8 inch in diameter and several hundred feet or morein length and wound on a spool generally indicated at 16. As seen in thecross-sectional view of FIG. 2, the welding electrode 14 comprises ahollow tubular sheath 14A formed of low carbon steel having aquantitative analysis such that no elements in the sheath 14A cause thelimits of the electrode chemistry to be described hereinafter to beexceeded. Tubular sheath 14A of electrode 14 serves as an envelope orcontainer for a core 14B formed of the various chemical elements of theelectrode, the elements in core 14B being in granular form. The spooledelectrode 14 may be supplied for use in a standard 55-pound package.Electrode 14 is threaded through drive rollers 18, driven by anysuitable drive means, which feeds the electrode through hollow nozzle 12at a predetermined controlled rate of speed, such as 100 inches perminute.

A suitable elevating and lowering mechanism diagrammatically indicatedat 30 (FIG. 1) and which forms no part of the present invention isconnected in operative relation to nozzle 12 as diagrammaticallyindicated by dotted line 30A and is effective to raise nozzle 12 and theelectrode 14 moving in nozzle 12 directly upwardly in properly timedrelation as the level of the weld deposit builds up, and also to lowernozzle 12 at the completion of a weld deposit, whereby to positionnozzle 12 and electrode 14 in readiness to begin another weld deposit onother workpieces.

A suitable direct current power supply diagrammatically indicated at 20is provided. An electrical conductor member 22 is connected at one endto the positive terminal of electrical power supply 20. The opposite endof conductor 22 is connected to an electrically conductive outlet guidemember 12A positioned at the discharge end of nozzle 12. Guide member12A is maintained in continuous electrical contact with the movingelectrode 14. The negative terminal of DC power supply 20 is suitablyconnected by conductor 24 to the steel workpiece 10A which is to bewelded to the steel workpiece 10B.

A suitable conducting member 26 underlies and is in contact with thelower end of the two workpieces 10A and 10B principally for the purposeof closing the lower end of gap G so that the molten metal of the welddeposit will not drop through the bottom of the gap. However, bridgingmember 26 also serves to provide an electrical connection betweenworkpiece 10B and workpiece 10A to which the negative side of the powersupply 20 is connected so that both workpieces 10A and 10B areelectrically connected from the very beginning of the welding operationto the negative side of power supply 20.

It can be seen that there is a difference of electrical potentialbetween welding electrode 14 and the two workpieces 10A and 10B.Typically, the difference in electrical potential between electrode 14and workpieces 10A, 10B provided by direct current power supply 20 is 38volts, with a typical current flow of 600 amperes during the electroslagwelding process.

As best seen in the view of FIG. 1, the weld deposit D is graduallybuilt up starting at the bottom end of the gap G between the twoworkpieces 10A and 10B, the heat of welding causing the wire-likewelding electrode 14 to melt and also causing a region indicated at 10A'and 10B' (FIG. 4) of each of the respective workpieces 10A and 10B toalso melt and to mix uniformly with the material of the weldingelectrode 14 to form a "puddle" of liquid metal M as indicated inFIG. 1. As the welding electrode 14 is gradually moved upwardly byelevating mechanism 30 from the lower end of gap G to the position shownin FIG. 1 which is intermediate the height of gap G, and also until thewelding electrode 14 has moved to the upper end of the gap G, there isalways a puddle of molten metal as indicated at M in FIG. 1 at the upperend of a deposit D of solidified solid metal below the puddle of liquidmetal. The puddle of molten metal M is typically about 2 inches deep.The solidified deposit D is referred to as the "weld deposit" or as the"weld nugget." Typically, when welding two members such as 10A and 10Bhaving a thickness T (FIG. 4) of 3 inches, and with a gap G which is11/4 inches wide, the level of the welding deposit will rise at a rateof 0.5 inches per minute when electrode 14 is being dispensed at therate of 100 inches per minute. Thus, with the assumed parameters justmentioned, it can be seen that 200 inches of electrode must be dispensedfor a rise of 1 inch in the height of the weld deposit.

During the welding operation, the bottom tip of the wire-like weldingelectrode 14 is always so positioned relative to the welding depositbeing formed that the bottom tip of the welding electrode is alwaysimmersed in the pool of molten slag S formed by the molten flux or"slag" which floats on the upper surface of the puddle of molten metalM.

Heat is evolved as the result of the passage of electrical currentthrough the pool of molten slag S, raising the temperature of the moltenslag S and of the puddle of molten metal M to a temperature in excess of2700 degrees F. The quantity of heat evolved is a function of thewelding voltage magnitude and of the welding current magnitude.

The flux is initially a dry powder-like material having a highpercentage of silicon (Si). The flux changes from its powder-likeinitial state to a molten state during the course of the welding processand when in the molten state the flux is referred to as "slag."

During the welding operation, the layer of molten flux or "slag"indicated at S and which typically is about 3/4 inch deep, always floatson the upper surface of the puddle of molten metal M. A welding fluxhaving "basic" (as opposed to acidic) characteristics is used and mayhave a typical nominal chemistry as follows, with the variousconstituents of the flux having the percentages by weight of the totalweight of the flux as indicated:

SiO₂ --25%-30%

CaO--17%

MnO--15%-25%

CaF₂ --30%-50%

Al₂ O₃ --2%

Fe₂ O₃ --2%

Basic fluxes of the general type just described are per se well known inthe art and are commercially available.

The welding flux F serves to prevent oxidation of the exposed verticalsurfaces 10AB, 10A'B' (FIG. 4) of the weld deposit, and also to preventoxidation of the upper surface 10A'C' of the weld deposit, all thesesurfaces being shown in the view of FIG. 4. The flux F also serves todeoxidize the molten metal M of the weld puddle, thereby formingrefractory-like oxides which form deposits of solidified slag on theoppositely-disposed outer surfaces 10AB and 10A'B' as seen in FIG. 2.When the molten slag S solidifies, the solidified slag which includesrefractory-like oxides is chipped off of the outer surfaces of thesolidified weld deposit or weld nugget D after the completion of thewelding operation.

A pair of vertically movable oppositely disposed shoes 36 are providedcontiguous the oppositely disposed lateral sides of gap G in the regionof and in bounding relation to the puddle of molten metal M and to thepool of molten slag S, whereby to prevent spillage of the molten metaland of the molten slag. Shoes 36 are operatively connected to elevatingand lowering mechanism 30 as diagrammatically indicated by the dottedline 30B, whereby shoes 36 are raised by mechanism 30B at the same rateas the upward movement of nozzle 12 and electrode 14, and whereby shoes36 are always at the proper level to retain the molten metal M andmolten slag S against spillage. Mechanism 30 also permits lowering ofshoes 36 at the completion of the weld deposit, whereby shoes 36 areagain properly located to retain the molten metal and the molten slagwhen another weld deposit is begun between two additional members to bewelded.

There is shown in FIGS. 3, 3A a pair of steel workpieces 50A and 50Bmade of steel of the family of steels which includes ASTM A516-76 (Grade70) and which are being welded together by an electroslag weldingprocess using a consumable nozzle in contrast to the method illustratedin FIG. 1 which employes a nonconsumable nozzle. It will be noted that astationary consumable nozzle generally indicated at 12' extendsvertically downwardly through gap G' between members 50A, 50B, and thata wire-like welding electrode 14, which is similar to the weldingelectrode 14 described hereinbefore in connection with the views ofFIGS. 1 and 2, extends downwardly through the hollow interior ofstationary consumable nozzle 12'.

Welding electrode 14 is unwound from a spool 16' and is threaded throughsuitable drive rollers 18', all in a manner similar to the arrangementdescribed in connection with the embodiment of FIG. 1. Shoes 36' areconnected to elevating and lowering mechanism 30' by the connectiondiagrammatically indicated at 30B', and shoes 36' are raised bymechanism 30' in properly timed relation whereby shoes 36' are always atthe proper level to retain molten metal M and molten slag S againstspillage, in the same manner as described in connection with theembodiment of FIG. 1. Welding electrode 14 is connected to the positiveside of direct current power supply 20', and workpieces 50A-50B areconnected to the negative side of power supply 20'.

The lower end 12A' of nozzle 12' and of welding electrode 14 withinnozzle 12' are immersed in the pool of molten slag S' which floats onthe upper surface of the pool of molten metal M' at the upper end of thesolidified weld deposit or weld nugget D', in the same manner asdescribed in connection with the nonconsumable nozzle arrangement ofFIG. 1. In the consumable nozzle method shown in FIG. 4, the consumablehollow nozzle 12' melts and forms part of the puddle of molten puddle M'so that by the time the weld deposit has built up to the level of theupper end of gap G' all of the portion of the stationary consumablenozzle 12' which is positioned in gap G' has melted into the graduallyrising puddle of molten metal M' at the upper end of the solidifieddeposit and has become part of the weld deposit. Since the consumablenozzle 12' of FIG. 4 is in substance a part of the electrode structureand the material of which consumable nozzle 12' is formed becomes partof the weld deposit, it follows that consumable nozzle 12' should bemade of an electrically conductive material such as low carbon steel andshould have no elements in its chemical composition which would causethe limits of the welding electrode chemistry of the present inventionto be hereinafter set forth to be exceeded, or which would otherwise beinconsistent with the chemistry of the welding electrode of the presentinvention.

DETAILED DESCRIPTION OF THE WELDING ELECTRODE AND ITS CHEMISTRY

Welding electrode 14 has particular utility for use in electroslagwelding although not necessarily restricted to use in electroslagwelding and is also particularly adapted for, although not restrictedto, use in the electroslag welding of steel members formed of low alloy,high tensile strength steels of the family of steels which includesAmerican Society of Testing Materials designations ASTM A516-76, ASTMA572-76, and ASTM A216-75. For purposes of brevity, this family ofsteels will hereinafter be referred to as "steels of the ASTM A516-76family."

Weld deposits No. N-17, No. N-18, and No. N-20 given hereinafter asExamples 1, 2, and 4 were all made on ASTM A516-76 (Grade 70) steelwhich has an ASTM description of "carbon steel plates for pressurevessels for moderate and lower temperature service."

Other steels in the ASTM A516-76 family include the following:

ASTM A572-76 having an ASTM description of "high strength low alloyColumbium-Vanadium steels of structural quality"

ASTM A216-75 (Grade WCC) having an ASTM description of "carbon steelcasting suitable for fusion welding for high temperature service"

The electroslag welding electrode 14 of the invention has the followingchemical composition:

    ______________________________________                                                        PERCENT OF TOTAL                                              CONSTITUENT     WEIGHT OF ELECTRODE                                           ______________________________________                                        Manganese (Mn)  About 1.90% to about 2.10%                                    Silicon (Si)    About 0.30% to about 0.45%                                    Nickel (Ni)     About 0.5% to about 1.5%                                                      but preferably about 0.9%                                                     to about 1.0%                                                 Carbon (C)      0.00% to about 0.05%                                          Phosphorus (P)  0.00% to about 0.02%                                          Sulfur (S)      0.00% to about 0.02%                                          Chromium (Cr)   0.00% to about 0.03%                                          Molybdenum (Mo) 0.00% to about 0.01%                                          Aluminum (A)    0.00% to about 0.01%                                          Copper (Cu)     0.00% to about 0.03%                                          Titanium (Ti)   0.00% to about 0.01%                                          Iron (Fe)       The remainder or balance                                                      of the total weight of                                                        the electrode is iron,                                                        and may be in the form                                                        of an iron powder.                                            ______________________________________                                    

The potential hydrogen content of the electrode shall be limited to ator under about ten parts per million (10.0 PPM). Oxygen in the electrodeshall be limited to at or under about 1500 parts per million (1500 PPM).

It will be noted that the chemical constituents of the welding electrode14 are manganese (Mn), silicon (Si), nickel (Ni), and iron (Fe), all inthe various percentages by weight of the total electrode weight of theelectrode 14 as given in the foregoing tabulation. In the illustratedembodiment shown in FIG. 2 of the drawings, the total weight ofelectrode 14 includes the weight of tubular sheath 14A and also theweight of core 14B of the electrode. Thus, the percent weight given inthe foregoing tabulation is the percent weight of the respectivechemical constituents relative to the weight of the total electrode,including the sheath 14A and the core 14B. As previously mentioned,sheath 14A is formed of low carbon steel having no elements therein inquantities such as to cause the limits of the electrode chemistry to beexceeded, since sheath 14A melts during the welding process and becomespart of the weld deposit D.

A very important feature of the inventive concept of the presentinvention is the fact that the carbon content of electrode 14 is reducedto the very minimum possible since the presence of carbon in theelectrode tends to lower the impact strength of the resulting welddeposit as measured by the Charpy impact test as will be describedhereinafter. Hence, reducing the carbon content of the welding electrode14 to the very minimum possible aids in providing greater impactstrength of the weld deposit. When the base metal which is being weldedis a low alloy, high tensile strength steel of the family of steels towhich ASTM A516-76 belongs, and having a relatively high carbon contenttherein, the effect of reducing to a minimum the carbon content of thewelding electrode is that substantially all, although not necessarilyentirely all, of the carbon content of the resulting electroslag welddeposit or weld "nugget" D is derived from the contribution of themelted base metal to the weld deposit, and there is a minimumcontribution of carbon from the welding electrode 14 to the resultingelectroslag weld deposit or weld nugget.

However, the minimization of the carbon content of the welding electrode14, as just explained and as set forth in the foregoing tabulation ofthe chemistry of the welding electrode, which results in increasing theimpact strength of the electroslag weld deposit would also normally tendto undesirably decrease the tensile strength of the resultingelectroslag weld deposit or weld nugget. It might be noted at this pointthat it is extremely essential that the tensile strength of theelectroslag weld deposit between two steel members being welded shouldnever be less than the ASTM specified minimum tensile strength of thesteel members being welded. Thus, for example, in welding two membersmanufactured of steel of the ASTM A516-76 (Grade 70) family which has anASTM specified minimum tensile strength of 70,000 PSI, it is absolutelyessential that the tensile strength of the electroslag weld deposit ornugget between such steel members should never be less than the ASTMspecified minimum tensile strength of the two steel members beingwelded, namely, that the tensile strength of the electroslag weld shouldnot, in this particular case, be less than 70,000 PSI. On the otherhand, the tensile strength of the electroslag weld deposit, in the casejust mentioned, can be greater than the ASTM specified minimum tensilestrength of the two steel members being welded (i.e., the tensilestrength of the weld deposit can be greater than 70,000 PSI).

It should be noted in this connection that if the workpieces are testedand found to have an actual tensile strength which is higher than theASTM specified minimum strength for the steel of which the workpiecesare made, it is acceptable for the electroslag weld deposit to have atensile strength which is less than the actual tensile strength of theworkpieces, as long as the tensile strength of the electroslag welddeposit is not less than the ASTM specified minimum tensile strength forthe steel workpieces.

For example, if the steel workpieces which are being welded are of ASTMA516-76 (Grade 70) steel having an ASTM minimum tensile strengthspecified at 70,000 PSI, and these workpieces are tested and found tohave an actual tensile strength of 75,000 PSI, in such case it isacceptable for the electroslag weld deposit between these workpieces tohave a tensile strength of 72,000 PSI which is less than the actualtensile strength of the workpieces but which is not less than the 70,000PSI ASTM minimum specified tensile strength of the workpieces.

A very significant feature of the chemical composition of the weldingelectrode as set forth in the foregoing tabulation is the presence ofnickel (Ni) in the electrode composition and in the percentage range setforth. The nickel in the electrode composition serves to compensate forthe loss of tensile strength of the electroslag weld deposit D whichwould otherwise be caused by reduction to a minimum of the carboncontent of the electrode. The presence of nickel in the electrodecomposition also serves to increase the impact strength of the resultingelectroslag weld deposit or weld nugget, reinforcing the improvement inimpact strength of the electroslag weld deposit which is provided by theminimal carbon content of the welding electrode as hereinbeforedescribed.

The nickel content of the welding electrode should not exceed about 1.5%of the total weight of the electrode since to exceed this percentagevalue might tend to promote solidification cracking of the resultingelectroslag weld deposit.

The manganese (Mn) content of the electrode as set forth in theforegoing tabulation serves three functions, as follows: (1) themanganese serves as a deoxidizer in the puddle of molten metal M formedby the molten electrode 14 and by the molten base members being welded,which molten puddle hardens to form the electroslag weld deposit D; (2)the manganese also serves to supplement the previously described effectof the nickel content of the electrode in increasing the tensilestrength of the resulting electroslag weld deposit to compensate for thedecrease in tensile strength which would otherwise be caused by theminimal carbon content of welding electrode 14; and (3) as in the casewith the nickel content of the welding electrode composition, themanganese content also tends to increase the impact strength of theresulting electroslag weld deposit to further supplement the increase inimpact strength of the weld deposit which is caused by the minimalcarbon content of the welding electrode.

The silicon content of the welding electrode 14 serves principally as adeoxidizer in the puddle of molten metal M which subsequently solidifiesinto the weld deposit, the presence of silicon in the welding electrodethereby helping to reduce the oxygen content of the resultingelectroslag weld to a value which is at or below the oxygen contentlimit of 1500 parts per million set forth in the foregoing descriptionof the chemistry of the welding electrode.

The remaining constituents (other than iron) listed in the foregoingtabulation of the chemistry of the welding electrode 14, namely,phosphorus (P), sulfur (S), chromium (Cr), molybdenum (Mo), aluminum(Al), copper (Cu), and titanium (Ti), are all contaminants whichsignificantly impair the integrity and mechanical quality of theresulting electroslag weld, and all of these last-mentioned elements aremaintained at the very minimal content possible in the welding electrode14, as set forth in the limits defined in the foregoing tabulation ofthe chemistry of welding electrode 14. The absence of these contaminantsfurther tends to enhance the impact and ductility properties of theelectroslag weld deposit. Potential hydrogen and oxygen as constituentsof the welding electrode are both also regarded as contaminants andshould be limited to maximum values of 10.0 parts per million potentialhydrogen and 1500 parts per million of oxygen in the welding electrodecomposition.

The sources of hydrogen contamination in the content of weldingelectrode 14 are such things as water moisture, rust, and oil. Hydrogencontent in the welding electrode should be held to a minimal value asset forth in the foregoing tabulation since the presence of hydrogencauses hydrogen embrittlement of the weld deposit which results in lossof ductility and loss of tensile strength of the resulting electroslagweld deposit or weld nugget. The presence of oxygen in the weldingelectrode should be held to a maximum value of 1500 parts per million asset forth hereinbefore since oxygen is also a contaminant which canadversely affect the quality of the weld deposit. For example, oxygencan combine with carbon to form carbon monoxide (CO) which tends tocause porosity of the weld deposit.

In examining the results of the spectrographic analysis on the variousspecimens of the base metal ASTM A516-76 (Grade 70) on which welddeposits N-17, N-18, and N20 were made, it will be noted that the basemetal contains only very small trace amounts of nickel so thatsubstantially all of the nickel in the resulting weld deposits N-17,N-18, and N-20 is derived from the nickel content of the electrode. Onthe other hand, an examination of the spectrographic analysis of thebase metal ASTM A516-76 (Grade 70) used in Examples 1, 2 and 4 (welddeposits N-17, N-18, and N-20) shows that there is a significantcontribution in the weld deposits of manganese (Mn) and silicon (Si)from the base metal. There is also a substantial contribution in theweld deposits of carbon from the base metal. It also might be noted thatsince silicon has a greater affinity than manganese for oxidation, arelatively greater portion of silicon than of manganese will be oxidizedduring the welding process.

As shown in FIGS. 13, 14 and 16, which are microphotographs of themicrostructures of the resulting electroslag weld deposits identified asNos. N-17, N-18 and N-20, using a welding electrode of the inventionhaving the chemistry as hereinbefore described, with all of the chemicalconstituents of the welding electrode being in the tolerance ranges setforth, and with the nickel content of the welding electrode being in thestated preferred range 0.9%-1.0% by weight of the total weight of theelectrode. Each of the weld deposits Nos. N-17, N-18, and N-20 wasrespectively formed between two steel members of ASTM A516-76 (Grade 70)steel. Each of the weld deposits N-17, N-18, and N-20 has the followingmetallurgical constituents:

(1) Fine acicular ferrite, indicated at FAF in the microphotographs;this is a metallurgical microstructure which contributes high impactcharacteristics to the weld deposit;

(2) Polygonal ferrite, indicated at PF in the microphotographs;

(3) A minimum of pearlite; polygonal ferrite and pearlite are both typesof metallurgical microstructures which are characteristic of welddeposits having low carbon content. There is inherently some pearlite inthe metallurgical structure of the weld deposits. In themicrophotographs, the pearlite is indicated at P.

(4) Proeutectoid ferrite having side plate formation; this is ametallurgical microstructure which imparts good ductilitycharacteristics to the weld deposit. In the microphotographs, theproeutectoid ferrite is indicated at PRO-F, and the side plate formationis indicated at SP.

(5) Absence of Widmanstatten formation; the absence of Widmanstattenformation is a good quality in the metallurgical microstructure of theelectroslag weld deposits since the presence of Widmanstatten formationcauses lower ductility and decreased impact strength in the welddeposit.

A microphotograph of weld deposit No. N-19 is shown in FIG. 15. Welddeposit No. N-19 was made on Allis-Chalmers Corporation designationACM-0015 steel and using the welding electrode of the invention havingthe chemistry as hereinbefore described, with all of the chemicalconstituents of the welding electrode being in the tolerance ranges setforth hereinbefore, and with the nickel content of the welding electrodebeing in the stated preferred range 0.9%-1.0% by weight of the totalweight of the electrode.

The metallurgical structure of weld deposit No. N-19 as shown in FIG. 15is generally similar to that just described in connection with welddeposits Nos. N-17, N-18, and N-20 of FIGS. 13, 14 and 16.

The characteristics of a metallurgical microstructure of the type justdefined and as shown in the microphotographs of FIGS. 13, 14, 15, and 16are described in the publication "DeFerri Metallographia--MetallographicAtlas of Iron, Steels and Cast Irons," Vols. I, II, III; published by W.B. Saunders Company, Philadelphia, London; Copyright 1966 by The HighAuthority of the European Coal and Steel Community, Luxemburg.

The wire-like welding electrode 14 described hereinbefore and shown incross-section in FIG. 2 may be defined as a "metal alloy core surroundedby a conductive sheath." In addition to having the chemical compositionof the electrode, as hereinbefore defined, in an electrode of the typejust mentioned and as shown in the cross-sectional view of FIG. 2, thewelding electrode of the invention could also be formed as a solidwire--that is, the chemical specification hereinbefore defined could becontained in an electrode of solid wire form. If the electrode of theinvention were to be required in a quantitatively large amount, it maybe more practical to manufacture the electrode in the form of a solidwire.

If the welding electrode is formed as a solid wire, then the totalweight of the electrode upon which the weight percentages of the variouschemical constituents are based is the weight of the solid wire.

The identical electrode 14 may be used interchangeably in both thenonconsumable nozzle method of FIG. 1 and in the consumable nozzlemethod of FIGS. 3 and 3a, and irrespective of whether the electrode isof the alloy sheath-core type shown in FIG. 2 or whether the electrodeis of the solid wire type. However, in using the consumable nozzlemethod of FIGS. 3 and 3a, a minor adjustment may have to be made in thewelding parameters such as joint gap and applied voltage whereby toadjust the dilution of the electroslag weld deposit, as describedhereinafter under the heading "Dilution of Electroslag Weld Deposit byBase Metal," to compensate for the fact that the material of theconsumable nozzle melts and becomes part of the weld deposit.

The various forms just described which the welding electrode may assumeare not intended to be restrictive as to the form which the weldingelectrode of the invention may assume since essentially it is onlynecessary that the welding electrode, whatever form it may assume,include the welding chemistry as hereinbefore set forth regardless ofwhat particular form the welding electrode may assume.

DESCRIPTION OF TESTS ON ELECTROSLAG WELDS

Tests were made on four different electroslag weld deposits,respectively identified as weld deposits No. N-17, No. N-18, No. N-19and No. N-20. In making each of the weld deposits No. N-17, No. N-18,No. N-19 and No. N-20, the welding electrode used was of the type shownin FIG. 2 of the drawings and manufactured to have an electrodechemistry according to the foregoing specification, with all of thechemical constituents of the welding electrode being in the toleranceranges set forth hereinbefore, and with the nickel content of thewelding electrode used in making each of the foregoing weld depositsbeing in the tolerance range 0.9% to 1.0% by weight of the totalelectrode weight. In making each of the weld deposits N-17, N-18, N-19and N-20, the wire-like welding electrode was fed through anonconsumable nozzle of the type shown in FIG. 1 of the drawings.

EXAMPLE 1

Weld deposit No. N-17 was made between two members formed of ASTMA516-76 (Grade 70) steel, of 31/2 inches thickness, and with a gap G11/4 inches wide between the members being welded. Weld deposit No. N-17has approximately a 40%-50% dilution of the electroslag weld deposit bythe base metal.

The following tests were conducted on the solidified electroslag welddeposit identified as No. N-17:

    ______________________________________                                        KSI = thousands of                                                            pounds per square inch                                                                         1/4 T       1/2 T                                            ______________________________________                                        Tensile strength in KSI                                                                        78.3        79.0                                             Yield strength in KSI                                                                          59.0        60.0                                             % Elongation     30.0        29.0                                             ______________________________________                                        Charpy Impact Tests on Weld Deposit No. N-17                                  At 30 deg F.                                                                  1/4 T            1/2 T                                                        Specimen Ft-Lbs.     Specimen   Ft.-Lbs.                                      ______________________________________                                        #1        59         #1         69                                            #2        90         #2         71                                            #3       117         .sup.1/83  87                                            #4       120         #4         102                                           #5       121         #5         146                                           Average = 101.4 Ft.-Lbs.                                                                       Average = 95 Ft.-Lbs.                                        AWS Average = 109 Ft.-Lbs.                                                                     AWS Average = 86.6 Ft.-Lbs.                                  ______________________________________                                        at 0 deg. F.                                                                  Specimen Ft.-Lbs.    Specimen   Ft.-Lbs.                                      ______________________________________                                        #1       44          #1         27                                            #2       75          #2         34                                            #3       79          #3         53                                            #4       79          #4         66                                            #5       102         #5         70                                            Average = 75.8 Ft.-Lbs.                                                                        Average = 50.0 Ft.-Lbs.                                      AWS Average = 77.6 Ft.-Lbs.                                                                    AWS Average = 51.0 Ft.-Lbs.                                  ______________________________________                                    

Bend tests conducted on electroslag weld deposit No. N-17 to helpevaluate the ductility of the weld deposit:

    ______________________________________                                        Sample No. Type of Bends  Results                                             ______________________________________                                        17-(1-1)   Side bends     No visible defects                                  17-(1-2)   Side bends     No visible defects                                  17-(1-3)   Side bends     No visible defects                                  17-(2-1)   Side bends     No visible defects                                  17-(2-2)   Side bends     No visible defects                                  17-(2-3)   Side bends     No visible defects                                  17-(3-1)   Side bends     No visible defects                                  17-(3-2)   Side bends     No visible defects                                  17-(3-3)   Side bends     No visible defects                                  ______________________________________                                    

The ASTM A516-76 (Grade 70) base metal on which electroslag weld No.N-17 was made, and also the electroslag weld deposit N-17 were bothsubjected to spectrographic analysis to determine the percentages byweight of the chemical constituents in the base metal and in the welddeposit, respectively, with the following results:

    ______________________________________                                        Spectrographic Analysis                                                                Base Metal                                                                    ASTM A516-76 Weld Deposit                                                     (Grade 70)   No. N-17                                                ______________________________________                                        C          0.29           0.07                                                Mn         1.06           1.80                                                P          0.008          0.007                                               S          0.029          0.009                                               Si         0.21           0.18                                                Ni         0.06           0.83                                                Cr         0.11           0.12                                                Mo         0.01           0.03                                                ______________________________________                                    

EXAMPLE 2

Weld deposit No. N-18 was made between two members formed of ASTMA516-76 (Grade 70) steel, of 31/2 inches thickness, and having a gap11/2 inches wide between the members being welded. Weld deposit No. N-18had approximately a 30%-40% dilution of the electroslag weld deposit bythe base metal.

The following tests were conducted on the solidified electroslag welddeposit No. N-18:

    ______________________________________                                                     KSI = thousands of pounds                                                     per square inch                                                                 18-A     18-B    18-C  18-D                                    ______________________________________                                        Tensile strength                                                              in KSI         78.8     80.3    79.3  79.6                                    Yield strength in KSI                                                                        60.2     60.5    60.2  60.7                                    % elongation   28.5     26.5    29.0  28.0                                    ______________________________________                                        Charpy Impact Tests on Weld Deposit No. N-18                                  at 30 deg. F.                                                                 1/4 T             1/2 T                                                       Specimen  Ft.-Lbs.    Specimen   Ft.-Lbs.                                     ______________________________________                                        #1         86         #1         77                                           #2        108         #2         86                                           #3        111         #3         92                                           #4        117         #4         114                                          #5        129         #5         120                                          Average = 110.2 Ft.-Lbs.                                                                        Average = 97.8 Ft.-Lbs.                                     AWS Average = 112.0 Ft.-Lbs.                                                                    AWS Average = 97.3 Ft.-Lbs.                                 ______________________________________                                        at 0 deg. F.                                                                  1/4 T             1/2 T                                                       Specimen  Fl-Lbs.     Specimen   Ft.-Lbs.                                     ______________________________________                                        #1        46          #1         52                                           #2        57          #2         54                                           #3        99          #3         83                                           #4        103         #4         102                                          #5        138         #5         134                                          Average = 88.6 Ft.-Lbs.                                                                         Average 85.0 Ft.-Lbs.                                       AWS Average = 86.3 Ft.-Lbs.                                                                     AWS Average = 79.6 Ft.-Lbs.                                 ______________________________________                                    

Bend tests conducted on electroslag weld deposit No. N-18 to helpevaluate the ductility of the weld deposit:

    ______________________________________                                        Sample No. Type of Bends  Results                                             ______________________________________                                        18-(1-1)   Side bends     No visible defects                                  18-(1-2)   Side bends     No visible defects                                  18-(1-3)   Side bends     No visible defects                                  18-(2-1)   Side bends     No visible defects                                  18-(2-2)   Side bends     No visible defects                                  18-(2-3)   Side bends     No visible defects                                  18-(3-1)   Side bends     No visible defects                                  18-(3-2)   Side bends     No visible defects                                  18-(3-3)   Side bends     No visible defects                                  ______________________________________                                    

The ASTM A516-76 (Grade 70) base metal on which electroslag weld depositNo. N-18 was made, and also the electroslag weld deposit No. N-18 wereboth subjected to spectrographic analysis to determine the percentagesby weight of the chemical constituents in the base metal and in the welddeposit, respectively, with the following results:

    ______________________________________                                        Spectrographic Analysis                                                                Base Metal                                                                    ASTM A516-76 Weld Deposit                                                     (Grade 70)   No. N-18                                                ______________________________________                                        C          0.29           0.06                                                Mn         1.06           1.58                                                P           0.008          0.011                                              S           0.029          0.011                                              Si         0.21           0.20                                                Ni         0.06           0.77                                                Cr         0.11           <0.11                                               Mo         0.01           0.03                                                ______________________________________                                    

EXAMPLE NO. 3

Weld deposit No. N-19 was made between two members formed ofAllis-Chalmers Corporation designation ACM-0015 steel. The ACM-0015steel is similar to ASTM A285-75 (Grade B) which has an ASTM description"pressure vessel plates, carbon steel, low and intermediate tensilestrength." The two members which were welded were of 2 inches thickness,and had a gap 11/2 inches wide between the members being welded. Welddeposit No. N-19 had approximately a 30%-40% dilution of the electroslagweld deposit by the base metal.

The following tests were conducted on the solidified electroslag welddeposit identified as No. N-19:

    ______________________________________                                                     KSI = thousands of pounds                                                     per square inch                                                                 19-A      19-B      19-C                                       ______________________________________                                        Tensile strength in KSI                                                                      75.1      71.5      71.6                                       Yield strength in KSI                                                                        57.2      42.5      40.5                                       % elongation   32.0      18.0      21.0                                       ______________________________________                                        Charpy Impact Tests on Weld Deposit No. N-19                                  at 30 deg. F.                                                                 Specimen         Ft.-lbs.                                                     ______________________________________                                        #1                76                                                          #2                79                                                          #3               101                                                          #4               120                                                          #5               127                                                          ______________________________________                                        at 0 deg. F.                                                                  Specimen         Ft.-lbs.                                                     ______________________________________                                        #1               62                                                           #2               70                                                           #3               71                                                           #4               92                                                           #5               103                                                          ______________________________________                                        at -25 deg. F.                                                                Specimen         Ft.-lbs.                                                     ______________________________________                                        #1               41                                                           #2               50                                                           #3               55                                                           #4               57                                                           #5               81                                                           ______________________________________                                    

Bend tests conducted on electroslag weld deposit No. N-19 to helpevaluate the ductility of the weld deposit:

    ______________________________________                                        Sample No. Type of Bends  Results                                             ______________________________________                                        19-(1-1)   Side bend      No visible defects                                  19-(1-2)   Side bend      No visible defects                                  19-(2-1)   Side bend      No visible defects                                  19-(2-2)   Side bend      No visible defects                                  19-(3-1)   Side bend      No visible defects                                  19-(3-2)   Side bend      No visible defects                                  19-(4-1)   Side bend      No visible defects                                  19-(4-2)   Side bend      No visible defects                                  ______________________________________                                    

The base metal on which electroslag weld deposit No. N-19 was made, andalso the electroslag weld deposit No. N-19 were both subjected tospectrographic analysis to determine the percentages by weight of thechemical constituents in the base metal and in the weld deposit,respectively, with the following results:

    ______________________________________                                        Spectrographic Analysis                                                                Base Metal                                                                    Allis-Chalmers                                                                             Weld Deposit                                                     ACM-0015     No. N-19                                                ______________________________________                                        C          0.19           0.06                                                Mn         0.47           1.50                                                P           0.007          0.008                                              S           0.032          0.012                                              Si         0.16           0.20                                                Ni         <0.01          0.65                                                Cr                        <0.10                                               Mo                        0.02                                                ______________________________________                                    

EXAMPLE 4

Weld deposit No. N-20 was made between two members formed of ASTMA516-76 (Grade 70) steel of 5 inches thickness, and with a gap G 11/2inches wide between the members being welded. Weld deposit No. N-20 hadapproximately a 50% dilution of the electroslag weld deposit by the basemetal.

The following tests were conducted on the solidified electroslag depositidentified as No. N-20:

    ______________________________________                                                 20-A     20-B     20-C   20-D   20-E                                 ______________________________________                                        Tensile                                                                       strength                                                                      in KSI   78.1     79.8     77.0   77.5   78.7                                 Yield                                                                         strength                                                                      in KSI   55.7     57.5     52.5   55.9   55.2                                 % elongation                                                                           27.0     28.5     39.0   40.0   38                                   ______________________________________                                        Charpy Impact Tests on Weld Deposit No. N-20                                  All Specimens Taken from 1/2 T Plane                                          at 30 deg. F.                                                                 Specimen         Ft.-lbs.                                                     ______________________________________                                        #1               28                                                           #2               33                                                           #3               48                                                           #4               66                                                           #5               75                                                           ______________________________________                                        at 0 deg. F.                                                                  Specimen         Ft.-lbs.                                                     ______________________________________                                        #1               14                                                           #2               17                                                           #3               19                                                           #4               33                                                           #5               67                                                           ______________________________________                                        at -25 deg. F.                                                                Specimen         Ft.-lbs.                                                     ______________________________________                                        #1               9                                                            #2               9                                                            #3               9                                                            #4               10                                                           #5               11                                                           ______________________________________                                    

Bend tests conducted on electroslag weld deposit N-20 to help evaluatethe ductility of the weld deposit:

    ______________________________________                                        Sample No. Type of Bends  Results                                             ______________________________________                                        20-(1-1)   Side bends     No visible defects                                  20-(1-2)   Side bends     No visible defects                                  20-(1-3)   Side bends     No visible defects                                  20-(1-4)   Side bends     No visible defects                                  20-(2-1)   Side bends     No visible defects                                  20-(2-2)   Side bends     No visible defects                                  20-(2-3)   Side bends     No visible defects                                  20-(2-4)   Side bends     No visible defects                                  20-(3-1)   Side bends     No visible defects                                  20-(3-2)   Side bends     No visible defects                                  20-(3-3)   Side bends     No visible defects                                  20-(3-4)   Side bends     No visible defects                                  20-(4-1)   Side bends     No visible defects                                  20-(4-2)   Side bends     No visible defects                                  20-(4-3)   Side bends     No visible defects                                  20-(4-4)   Side bends     No visible defects                                  ______________________________________                                    

The base metal on which electroslag weld deposit No. N-20 was made, andalso the electroslag weld deposit No. N-20 were both subjected tospectrographic analysis to determine the percentages by weight of thechemical constituents in the base metal and in the weld deposit,respectively, with the following results:

    ______________________________________                                        Spectrographic Analysis                                                                Base Metal                                                                    ASTM A516-76 Weld Deposit                                                     (Grade 70)   No. N-20                                                ______________________________________                                        C          0.28           0.15                                                Mn         0.99           1.47                                                P           0.011          0.011                                              S           0.029          0.011                                              Si         0.21           0.17                                                Ni         <0.06          0.49                                                Cr         <0.11          <0.11                                               Mo         <0.01          0.02                                                V          <0.01          0.01                                                Cb*        <0.01          <0.01                                               Al          0.023         <0.003                                              Ti         <0.01          <0.01                                               ______________________________________                                         *Columbium                                                               

The following comments are pertinent with respect to the foregoing testresults on weld deposits No. N-17, N-18, N-19 and N-20:

It will be noted that the test results for weld deposit No. N-17 in thetabulation of results for tensile strength, yield strength and %elongation, there are two column headings as follows: "1/4T" and "1/2T."From an examination of FIG. 4 of the drawings, it will be noted that"1/4T" and "1/2T" designate the vertical planes in electroslag welddeposit No. N-17 from which the respective round tensile specimens 60Aand 60B for use in performing the tensile strength, yield strength and %elongation tests made on weld deposit No. N-17 were obtained. Thus, theround tensile specimen indicated at 60A in FIG. 4 was removed from thevertical plane indicated at "1/4T" and the round tensile specimenindicated at 60B in FIG. 4 was removed from the "1/2T" vertical plane ofthe electroslag weld deposit No. N-17. The round tensile specimens 60Aand 60B are of the type illustrated by the specimen 60 in FIG. 6 of thedrawings. It will be understood that more than one round tensilespecimen may be removed from each of the respective vertical planes1/4T, 1/2T.

FIG. 7 illustrates the manner in which the specimens used in the sidebend tests for the weld deposits N-17, N-18, N-19 and N-20 wereobtained. Thus, it will be noted that three immediately verticallysuperposed layers or "slices" of material are cut from the electroslagweld deposit, these respective layers in FIG. 7 being identified as A, Band C. Each of the layers or "slices" of a given weld deposit are thencut into strips such as those indicated at 17-(1-1), 17-(1-2), and17-(1-3) of the layer or "slice" indicated at "A" in FIGS. 7 and 8. Theuppermost layer A thus serves as a source for the side bend specimen17-(1-1), specimen 17-(1-2) and specimen 17-(1-3). Similarly, the layerdesignated at B provides the side bend specimens 17-(2-1), 17-(2-2) and17-(2-3); and in a similar manner, the layer indicated at C in FIG. 7provides the side bend specimens 17-(3-1), 17-(3-2) and 17-(3-3). FIG. 8is a perspective view of one of the layers such as the layer A of FIG. 7which is cut as shown in FIG. 8 into the three specimens 17-(1-1),17-(1-2) and 17-(1-3). The side bend specimens from weld deposits N-18,N-19 and N-20 were obtained in a similar manner to that just described.

FIG. 9 illustrates a slice taken from weld deposit N-17 in a mannersimilar to the previously-described slices A, B and C with two of thespecimens indicated at 62A, 62B on which Charpy impact tests wereperformed being removed from slice D.

Thus, the Charpy impact test specimen indicated at 62B is cut from sliceD at a location such that weld specimen 62B has its centerline lying inthe vertical plane indicated at 1/2T which lies in the center of thefront-to-rear dimension of the slice D and of the electroslag welddeposit N-17. The Charpy impact test specimen indicated at 62A has itscenterline lying in the vertical plane indicated at 1/4T which isone-fourth the distance from the rear to the front (relative to the viewof FIG. 9) of the slice D and of the electroslag weld deposit shown inFIG. 9. The two specimens 62A and 62B of FIG. 9 are similar to thespecimen indicated at 62 in FIG. 10. Specimens of the type indicated inFIGS. 9 and 10 were also used in the Charpy impact tests performed onweld deposits Nos. N-18, N-19 and N-20. The Charpy impact test specimensfor weld deposit No. N-18 were taken from the planes 1/4T and 1/2T asindicated in the test data for weld No. N-18. The Charpy impact testspecimens for weld deposit No. N-19 were taken from planes of welddeposit No. N-19 such as 1/4T and/or 1/2T as indicated in FIG. 9. TheCharpy impact test specimens for weld deposit No. N-20 were all takenfrom the vertical plane 1/2T of weld deposit N-20.

Round tensile specimens of the type illustrated in FIGS. 4 and 6 such asthe specimens indicated at 60A and 60B in FIG. 4 and at 60 in FIG. 6were used on all of the tensile strength, yield strength and %elongation tests for both the weld deposits N-17 and N-18, for the testsunder the column heading "19A" in Example 3 for weld deposit No. N-19,and also for the tensile tests under the column headings 20A, 20B madeon weld deposit No. N-20. However, the tensile strength test, the yieldstrength test and the % elongation results under the column headings"19-B" and "19-C" for weld deposit No. N-19 and under the columnheadings 20-C, 20-D and 20-E for weld deposit No. N-20 were performed ona reduced section tensile specimen of the type shown in FIGS. 11 and 12.

FIGS. 11 and 12 illustrate the location and type of reduced sectiontensile specimen used in connection with the tensile strength test, theyield strength test and the % elongation test tabulated under the columnheadings 19-B and 19-C of Example 3 relating to weld deposit No. N-19and under the column headings 20-C, 20-D, 20-E relating to weld depositNo. N-20. Thus, as seen in FIG. 11, the reduced section tensile specimenindicated at 64 in FIG. 11 lies along the centerline 1/2T of slice E andof the electroslag weld deposit shown in FIG. 11. A perspective view ofthe specimen indicated at 64 is shown in FIG. 12.

It might be noted that in connection with each of the Charpy impacttests for the weld deposits No. N-17 and N-18 two "averages" are given.Thus, for example, considering the first set of Charpy impact tests madeon weld deposit No. N-17 at 30 degrees F. on the specimens taken fromalong the 1/4T line (FIG. 9): one average is obtained by adding all ofthe readings in ft.-lbs. for the five test specimens Nos. 1-5,inclusive, and then dividing by 5 to give the "average"=101.4 ft.-lbs.The other average which is referred to as the "AWS Average" is obtainedin accordance with the standards set forth by the American WeldingSociety by discarding the low reading and the high reading of the Charpyimpact test results on the five specimens and then taking the average ofthe three remaining readings. By utilizing this method of obtaining anaverage, the result "AWS Average"=109 ft.-lbs. is obtained. This isillustrative of the manner of obtaining the two averages given inconnection with the various Charpy impact tests on the various welddeposits.

The various tests hereinbefore described were conducted in accordancewith procedures and standards set up as follows:

The tests on tensile strength, yield strength and % elongation and theside bend tests were conducted in accordance with standards andprocedures set forth in the American Society of Mechanical EngineersBoiler and Pressure Vessel Code, Section IX, QW-462.1(a), 1977, andSection IX, QW-466, 1977.

The Charpy Impact Tests were conducted in accordance with procedures andstandards set forth in American Society of Mechanical Engineers Boilerand Pressure Vessel Code, Subsection A-General Requirements-SectionVIII, Division 1, 1977 edition. All of the foregoing American Society ofMechanical Engineers publications are published by the American Societyof Mechanical Engineers, 345 East 47th Street, New York, New York 10017.

The standards and procedures for conducting the Charpy Impact Testswhich were conducted are also set forth in the "Structural Welding Code"of the American Welding Society, (AWS D.1-1), Appendix C, entitled"Impact Strength Requirements for Electroslag and Electrogas Welding,"1976 revisions, published by the American Welding Society, Inc., 2501N.W. 7th Street, Miami, Florida 33125.

It might be noted that the yield strength or yield point of theelectroslag weld deposit is the tensile stress in pounds per square inchat which elongation of the test specimen first occurs. The yield pointcorresponds to the point Y on the stress-strain curve of FIG. 5.

The tensile strength of the electroslag weld as set forth in theforegoing test results is the peak or maximum value of tensile strengthdetermined during the application of tensile stress on the test specimenand corresponds to the point T in the stress-strain curve of FIG. 5 ofthe drawings.

The percent elongation of the electroslag weld deposits as measured bythe foregoing test results is the percentage increase in length of thetest specimen at the time when fracture of the test specimen such as thespecimen 60 of FIG. 6 or the specimen 64 of FIG. 12 occurs (i.e.,elongation of the specimen at the time of fracture as compared to theoriginal length of the specimen). The percentage elongation of thespecimen is an indication of the ductility of the electroslag weld. Thebend tests are also an indication of the ductility of the electroslagweld.

It will be noted that weld deposits N-17, N-18 and N-20 were made onASTM A516-76 (Grade 70) steel. The test results indicate thatelectroslag weld deposits N-17, N-18 and N-20 made using the electrodeof the invention are of such high quality with respect to the impactstrength, tensile strength, and ductility of these weld deposits that nopost-weld high temperature "normalizing" heat treatment of these welddeposits is necessary, as would have been required using weldingelectrodes of the prior art.

It will be noted that weld deposit N-19 was made on steel havingAllis-Chalmers Corporation designation ACM-0015 which is similar to ASTMA-285, grade B steel having a nominal ASTM minimum tensile strengthrating of 50,000 PSI. While prior art welding electrodes have been knownwhich when used on steel such as Allis-Chalmers Corporation ACM-0015have resulted in weld deposits having mechanical properties which wereacceptable without the necessity of post-weld "normalizing" heattreatment, the test results in weld deposit No. N-19 on the ACM-0015steel indicate that weld deposit No. N-19 made with the weldingelectrode of the present invention is superior in mechanical qualitiessuch as impact strength, tensile strength, and ductility to welds madeon this type of steel with welding electrodes of the prior art.

None of the weld deposits N-17, N-18, and N-20 hereinbefore described orthe steel members joined by these weld deposits was given any hightemperature "normalizing" post-weld heat treatment of the type used inthe prior art to obtain acceptable mechanical properties in electroslagweld deposits made on steels of the ASTM A516-76 family, as described inthe introductory portion of this specification. Also, no "normalizing"post-weld heat treatment was used in weld deposit N-19 which was made onAllis-Chalmers designation ACM-0015 steel, or on the steel members,joined by weld deposit N-19. However, all of the weld deposits N-17,N-18, N-19, and N-20 and the steel members joined by these weld depositswere subjected to a post-weld stress-relief heat treatment at atemperature of 1150 degrees F. to equalize the tensile and compressivestresses set up during the welding operation as described in theintroductory part of this specification.

Dilution of Electroslag Weld Deposit by Base Metal

It has been previously pointed out that the molten puddle of metal whichsubsequently solidifies into the electroslag weld deposit is formed notonly from the molten welding electrode material but is also formed byportions of the base metal (i.e., the metal being welded) which meltsduring the electroslag welding process and forms part of the moltenpuddle which becomes the solidified weld deposit. Thus, as explained inconnection with the view of FIG. 4, the areas indicated at 10A' and 10B'in FIG. 4 represent regions of the original base metal which have meltedduring the welding process and have formed part of the weld deposit, themelted material of the base metal being uniformly distributed throughoutthe entire volume of the weld deposit, and with the resulting welddeposit filling the regions indicated at 10A' and 10B' which wereformerly occupied by the base metal of the members 10A and 10B which arebeing welded.

The "percent dilution" of a given electroslag weld deposit is thepercent of the weight of the electroslag weld deposit which iscontributed by the base metal (i.e., the members such as 10A and 10B ofFIG. 1) which are being welded. Thus, for example, a "20% dilution"means that 20% of the total weight of the electroslag weld deposit iscontributed by the material of the base metal and that the remaining 80%of the total weight of the electroslag weld deposit is contributed bythe material of the welding electrode.

The chemical composition of the welding electrode of the invention, aspreviously defined hereinafter, is particularly adapted for use in adilution range of 30%-40% when operating on base metals of the ASTMA516-76 family as previously defined. A dilution range of 30%-40% isconsidered the optimum range of dilutions from the standpoint of ease ofproduction when operating on this family of steels (i.e.--from thewelding operator's viewpoint), although a dilution range of 20%-30% ispreferable from the standpoint of obtaining optimum mechanicalproperties in the weld deposit. However, the welding electrode of theinvention, as hereinbefore defined, has a chemical composition such thatthe electrode will provide acceptable electroslag weld deposits,although not always necessarily optimum electroslag weld deposits, overa range of dilutions from 10% to 60%.

The nominal chemistry of ASTM A516-76 (Grade 70) steel has maximum andminimum tolerance limits on the chemical composition thereof and thefollowing table is a table of calculated welding deposit chemistriesunder four different dilution conditions at which acceptable welddeposit chemistries are obtained as follows:

(1) 40% dilution of anticipated maximum tolerance ASTM A516-76 (Grade70) steel;

(2) 20% dilution of anticipated maximum tolerance ASTM A516-76 (Grade70) steel;

(3) 40% dilution of anticipated minimum tolerances ASTM A516-76 (Grade70) steel; and

(4) 20% dilution of anticipated minimum tolerance ASTM A516-76 (Grade70) steel.

In making the following computations, aluminum in the weld deposit hasbeen factored by 0.5 to allow for normal oxidation during welding.

                  TABLE 1                                                         ______________________________________                                        Weld Deposit Chemistry                                                                          Anticipated                                                 at 40% Dilution   A516-76 (Grade 70) max.                                     ______________________________________                                        C-0.14            C-0.31                                                      Mn-1.70           Mn-1.25                                                     Si-0.32           Si-0.21                                                     Ni-0.70           Ni-0.25                                                     Cr-0.08           Cr-0.16                                                     Mo-0.03           Mo-0.07                                                     Al-0.012          Al-0.043                                                    Cu-0.10           Cu-0.22                                                     ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Weld Deposit Chemistry                                                                          Anticipated                                                 at 20% Dilution   A516-76 (Grade 70) max.                                     ______________________________________                                        C-0.087           C-0.31                                                      Mn-1.85           Mn-1.25                                                     Si-0.36           Si-0.21                                                     Ni-0.85           Ni-0.25                                                     Cr-0.05           Cr-0.16                                                     Mo-0.02           Mo-0.07                                                     Al-0.008          Al-0.043                                                    Cu-0.07           Cu-0.22                                                     ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Weld Deposit Chemistry                                                                          Anticipated                                                 at 40% Dilution   A516-76 (Grade 70) min                                      ______________________________________                                        C-0.09            C-0.19                                                      Mn-1.52           Mn-0.80                                                     Si-0.29           Si-0.13                                                     Ni-0.60           Ni-0.01                                                     Cr-0.02           Cr-0.01                                                     Mo-0.014          Mo-0.02                                                     Al-0.019          Al-0.08                                                     Cu-0.026          Cu-0.02                                                     ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Weld Deposit Chemistry                                                                          Anticipated                                                 at 20% Dilution   A516-76 (Grade 70) min.                                     ______________________________________                                        C-0.056           C-0.19                                                      Mn-1.76           Mn-0.80                                                     Si-0.34           Si-0.13                                                     Ni-0.80           Ni-0.01                                                     Cr-0.02           Cr-0.01                                                     Mo-0.012          Mo-0.02                                                     Al-0.012          Al-0.08                                                     Cu-0.028          Cu-0.02                                                     ______________________________________                                    

All of the foregoing tables 1, 2, 3 and 4 are based upon the assumptionthat the welding electrode has an electrode chemistry in accordance withthe electrode chemistry of the invention as previously defined,including a nickel content of 0.9%-1.0%. Tables 1 and 2 assume that theelectroslag weld deposit is made on a base member of ASTM A516-76 (Grade70) steel in which the various chemical constituents of the steel are atthe maximum or upper end of the range of their nominal range oftolerances. Table 1 shows the calculated weld deposit chemistry at 40%dilution, and Table 2 shows the calculated weld deposit chemistry at 20%dilution.

Tables 3 and 4 assume that the electroslag weld deposit is made on basemembers of ASTM A516-76 (Grade 70) steel in which the various chemicalconstituents of the steel are at the lower end or minimum end of theirnominal range of tolerances. Table 3 shows the calculated weld depositchemistry at 40% dilution and Table 4 shows the calculated weld depositchemistry at 20% dilution.

Dilution of the electroslag weld deposit can be controlled approximatelyby (1) control of the joint gap between the members being welded(i.e.--the wider the joint gap, the lower the percent dilution, and thenarrower the joint gap, the greater the percent dilution; (2) by controlof the welding voltage; by increasing the welding voltage, the percentdilution is increased; by reducing the welding voltage, the percentdilution is reduced; and (3) by a combination of the controls (1) and(2) just enumerated. However, the factors just mentioned are difficultto precisely control due to meter errors in measuring applied voltageand also due to dimensional tolerances of the members being welded, andadditionally, because of human errors.

In connection with the foregoing discussion of the dilution of theelectroslag weld deposit by the base metal which is being welded, itmight be mentioned that some workers in the electroslag welding art havetaught that the percent dilution of the electroslag weld by the basemetal should be purposely kept at a low value such as 5%-10% in order tolimit the carbon content of the resulting electroslag weld. However, itis difficult to consistently obtain such a low dilution range as thatjust mentioned, and furthermore various problems occur when such a lowweld dilution range is attempted.

While the welding electrode of the invention has been described as beingused in connection with an electroslag welding process and hasparticular utility when used in such process, it is also within thescope of the present invention to utilize the welding electrode of theinvention in other types of welding processes, such as, for example, inan electric arc welding process.

From the foregoing detailed description of the invention, it has beenshown how the objects of the invention have been obtained in a preferredmanner. However, modifications and equivalents of the disclosed conceptssuch as readily occur to those skilled in the art are intended to beincluded within the scope of this invention.

The embodiments of the invention in which an exclusive property ofprivilege is claimed are defined as follows:
 1. The method ofelectroslag welding steel members of the ASTM A516-76 family whichcomprises the steps of (1) positioning said steel members to have ajoint gap therebetween prior to the welding operation, (2) using inassociation with a welding flux a welding electrode having the followingalloying constituents by percent weight of the weight of the totalelectrode:About 1.90% to about 2.10% manganese About 0.30% to about0.45% silicon About 0.5% to about 1.5% nickel,and in which the weight ofthe carbon content of said welding electrode does not exceed about 0.05%of the total weight of said electrode, and in which substantially theentire balance of the weight of said electrode is iron; (3) applying adirect current voltage between said electrode and said steel memberswhereby to cause said electrode and a portion of said steel memberscontiguous said joint gap to melt to form a puddle of molten metal, witha puddle of molten slag formed by said welding flux being superposedabove said puddle of molten metal, with the joint gap between sald steelmembers and the applied direct current voltage between said electrodeand said steel members being parameters which may be controlled tocontrol the percentage dilution of the electroslag weld deposit; and (4)correlating the values of said parameters to obtain a dilution of saidelectroslag weld deposit in the range of about 20% to about 50%.
 2. Themethod of electroslag welding defined in claim 1 in which the nickelcontent of said electrode has a weight which is about 0.9% to about 1.0%of the total weight of said electrode.
 3. The method of electroslagwelding defined in claim 1 in which the chemical composition of saidelectrode is such that said electrode is particularly adapted for use ina dilution range of 30%-40%.
 4. The method of electroslag welding steelmembers of the ASTM A516-76 family which comprises the steps of (1)positioning said steel members to have a joint gap therebetween prior tothe welding operation, (2) using in association with a welding flux awelding electrode having the following alloying constituents by percentweight of the weight of the total electrode:About 1.90% to about 2.10%manganese About 0.30% to about 0.45% silicon About 0.5% to about 1.5%nickel,and in which the weight of the carbon content of said weldingelectrode does not exceed about 0.05% of the total weight of saidelectrode, and in which the respective weights of the following elementsdo not exceed the following percentages of the weight of the totalelectrode: Phosphorus: about 0.02% Sulfur: about 0.02% Chromium: about0.03% Molybdenum: about 0.01% Aluminum: about 0.01% Copper: about 0.03%Titanium: about 0.01%and in which the hydrogen content of said electrodedoes not exceed about 10.0 parts mer million and the oxygen content ofsaid electrode does not exceed about 1500 parts per million; and inwhich substantially the entire balance of the weight of said electrodeis iron, and (3) applying a direct current voltage between saidelectrode and said steel members whereby to cause said electrode and aportion of said steel members contiguous said joint gap to melt to forma puddle of molten metal, with a puddle of molten slag formed by saidwelding flux being superposed above said puddle of molten metal, withthe joint gap between said steel members and the applied direct currentvoltage between said electrode and said steel members being parameterswhich may be controlled to control the percentage dilution of theelectroslag weld deposit; and (4) correlating the values of saidparameters to obtain a dilution of said electroslag weld deposit in therange of about 20% to about 50%.